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  3. Information about tiger sharks is rare in books so most of this paper about sharks will be in general. The Tiger Sharks’ Latin n

Information about tiger sharks is rare in books so most of this paper about sharks will be in general. The Tiger Sharks’ Latin n

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问题     Information about tiger sharks is rare in books so most of this paper about sharks will be in general. The Tiger Sharks’ Latin name is Galeocerdo Cuvier. Sharks are a member of the fish family. There are over 350 species of sharks. Sharks can be as big as 49 feet long (whale shark) and as short as 6 inches (cigar shark). Sharks’ bodies do not have bones, but have cartilage (软骨) instead. They have pointed heads with five gills (鳃) behind it. Sharks have very sharp teeth that are replaced whenever they lose teeth. Sharks’ skin can be reddish brown, bronze, metallic blue or nearly black, although most of them are gray. Some have spots, bands and marbling. Their skin is leathery (粗糙) and covered with small pointed scales (鳞) which are so sharp that if petted in the opposite direction can actually hurt your hand.
    Sharks have great senses. Their eyes are sensitive and can even see in dim light. Their sense of smell is outstanding. They also have senses that humans do not. Sharks can feel when other things are around them. Also, they have organs on their snouts (鼻子) which tell them when other fish are around. Sharks are known to eat every creature in the sea including their own kind. Some sharks eat only plants and plankton (浮游生物). Others prefer live food. People have found very unusual things in sharks’ stomachs such as hooves of cows, horses, dogs, cats, goats and human corpses.
    Unlike bony fish which lay hundreds of eggs at one time, sharks’ litters are much smaller. Some sharks have as few as two offspring at a time. Bony fish babies are born small and puny. Shark "pups" are born fully developed and are ready to eat the foods that full-grown sharks eat.
    Some of sharks’ behavior is interesting and understood. Other behaviors are still mysterious. For example, sharks attack when they are hungry. But why they attack when they are not hungry, we do not know. They may attack for defense, because they think humans are food, because they smell blood or because they smell or sense chemicals that are interesting to them. While people may think that all sharks are dangerous, only about 30 species are considered dangerous, including the Tiger Shark. Even when sharks do attack, the victims usually do not die anyway.
    Sharks are found in all of the world’s oceans although most of them prefer to live in tropical waters. A very few species live in waters as cold as the Antarctic Ocean. Sharks live at all depths of the oceans. Because sharks are so adaptable there are many of them all around the world, living in all of our oceans.
   Here are some interesting facts about tiger sharks:
    Shark eggs have strings attached to them. The strings hook onto corals or seaweed so the egg will not drift off. All baby sharks are called pups. Sharks are one of the oldest species of animals and have been on earth for about three million years.
    Sharks’ only natural predator (猎食者) is sharks.
    Unlike bony fish, sharks do not have air bladders (囊) and so if they stop swimming , they will sink to the bottom.
    The largest organ in the shark’s body is its liver. Sharks can survive without food for long periods of time because they can live off the oil of their fiver.
    People use many products that come from sharks such as oil, vitamins, fertilizer and leather. Some people also like to collect shark teeth and jaws. Shark meat is becoming a more popular food in the United States.
How do sharks survive without food for a long time?
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答案They can live off the oil of their liver．
解析 原文倒数第二段最后一句提到"Sharks can survive without food for long periods of time because they can live off the oil of their liver"。
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